An interframe predictive coding technology includes a plurality of coding technologies that are based on a candidate motion information set, such as a merge mode coding technology and an advanced motion vector prediction technology. A common point of these technologies is that these technologies construct a candidate motion information set for an image block currently under coding and decoding processing (which is called a current block for short), and select a piece of motion information from the candidate motion information set as motion information of the current block or as a predictive value of motion information of the current block. The motion information may include a motion vector and a predictive direction, and other information such as a reference image index. To enable a decoding end to obtain motion information selected by a coding end, the coding end needs to transmit the selected information to the decoding end. The coding end and the decoding end construct a candidate motion information set in the same way as the coding end; therefore, the decoding end can select, according to the received information about motion information selection and from the candidate motion information set, the same motion information as that of the coding end for a motion compensation operation. Motion information of a space adjacent block may be used when the candidate motion information set of the current block is constructed, in other words, the candidate motion information set of the current block can be constructed only after motion information of the space adjacent block has been determined. As a result, the coding technology based on the candidate motion information set cannot be simultaneously used for more than one image block.